Non-aqueous electrolyte secondary battery

Abstract

In this non-aqueous electrolyte secondary battery: a positive electrode active material contains a lithium transition metal oxide that has a layered structure including a Li layer and that contains at least prescribed amounts of Ni, Ca, and Al; the proportion of metal elements, excluding Li, in the Li layer is 0.6-2.0 mol % with respect to the total number of moles of metal elements, excluding Li, contained in the lithium transition total oxide; a negative electrode active material has a coating containing Ca on the surface thereof; and the contained amount of Ca in the coating is not less than 15 mass ppm but less than 80 mass ppm with respect to the total mass of the positive electrode material.

The invention claimed is: 
     
       1. A non-aqueous electrolyte secondary battery comprising:
 a positive electrode including a positive electrode active material; 
 a negative electrode including a negative electrode active material; and 
 a non-aqueous electrolyte, wherein 
 the positive electrode active material includes a lithium transition metal oxide having a layered structure including a Li layer in which Li reversibly moves in and out, and including at least Ni, Ca and Al; 
 in the lithium transition metal oxide, 
 a content of Ni is 80 mol % or more and 95 mol % or less relative to a total amount of metal elements excluding Li; 
 a content of Ca is more than 0 mol % and 3 mol % or less relative to the total amount of metal elements excluding Li; 
 a content of Al is more than 0 mol % and 8 mol % or less relative to the total amount of metal elements excluding Li; 
 a proportion of metal elements excluding Li present in the Li layer is 0.6 mol % or more and 2.0 mol % or less with respect to a total number of moles of metal elements excluding Li included in the lithium transition metal oxide; 
 the negative electrode active material comprises a film including Ca on a surface thereof; and 
 a proportion of Ca in the film is 15 ppm by mass or more and less than 80 ppm by mass relative to a total mass of the positive electrode active material. 
 
     
     
       2. The non-aqueous electrolyte secondary battery according to  claim 1 , wherein the negative electrode active material further includes Ni in the film. 
     
     
       3. The non-aqueous electrolyte secondary battery according to  claim 2 , wherein a molar ratio of a content of Ca to a content of Ni in the film is 0.5≤Ca/Ni≤1.0.